The present invention relates to an apparatus for monitoring irregularities and/or changes in the structure of a textile yarn coming from an open-end spinning turbine, the monitoring apparatus being of the type which includes a measuring value sensor to sense irregularities and an evaluation circuit which, upon the occurrence of irregularities, generates a signal to actuate an indicator and/or to switch off the spinning turbine.
Such an apparatus is disclosed in German Offenlegungsschrift [laid-open application] No. 2,509,259. In that apparatus, a sensor is provided in the yarn removal path to generate an analog signal which is representative of the thickness of the yarn. A pulse is generated each time this analog signal exceeds or drops below threshold values, i.e., when the thickness of the yarn is above or below a selected range, and the resulting pulses are counted in a counter, the occurrence of at least a given number of pulses within a given period of time causing a display or switch-off signal to be emitted.
Monitoring of the yarn being produced in an open-end spinning machine is recommended because irregularities, particularly thickness variations in the yarn may occur irregularly in cycles or even at regular intervals and thus would lead to undesirable moire effects in fabrics produced from that yarn.
Such thicker or thinner portions are produced mainly as a result of deposits of dirt particles in the rotor of the spinning turbine, and additionally by other causes.
The yarn may also exhibit changes in its structure.